1 //===----------------------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef _LIBCPP___ALGORITHM_HALF_POSITIVE_H
10 #define _LIBCPP___ALGORITHM_HALF_POSITIVE_H
11 
12 #include <__config>
13 #include <__type_traits/enable_if.h>
14 #include <__type_traits/is_integral.h>
15 #include <__type_traits/make_unsigned.h>
16 
17 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
18 #  pragma GCC system_header
19 #endif
20 
21 _LIBCPP_BEGIN_NAMESPACE_STD
22 
23 // Perform division by two quickly for positive integers (llvm.org/PR39129)
24 
25 template <typename _Integral, __enable_if_t<is_integral<_Integral>::value, int> = 0>
__half_positive(_Integral __value)26 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Integral __half_positive(_Integral __value) {
27   return static_cast<_Integral>(static_cast<__make_unsigned_t<_Integral> >(__value) / 2);
28 }
29 
30 template <typename _Tp, __enable_if_t<!is_integral<_Tp>::value, int> = 0>
__half_positive(_Tp __value)31 _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR _Tp __half_positive(_Tp __value) {
32   return __value / 2;
33 }
34 
35 _LIBCPP_END_NAMESPACE_STD
36 
37 #endif // _LIBCPP___ALGORITHM_HALF_POSITIVE_H
38